Recently, portable electronic devices have become rapidly small and light, so that a demand for a small and high capacity battery used as a driving power source thereof has increased. Particularly, an operational voltage of a lithium rechargeable battery has 3.6 V or more, which is three times higher than that of a nickel-cadmium battery or a nickel-hydrogen battery widely used as a power source of a portable electronic device, and the energy density per unit weight thereof is high, so that the lithium rechargeable battery has rapidly expanded.
The lithium rechargeable battery generates electric energy by oxidation and reduction reactions when lithium ions are intercalated and deintercalated in a positive electrode and a negative electrode. The lithium rechargeable battery uses a material, which is capable of reversibly intercalating and deintercalating lithium ions, as an active material of the positive electrode and the negative electrode, and is manufactured by charging an organic electrolyte or a polymer electrolyte between the positive electrode and the negative electrode.
The lithium rechargeable battery includes an electrode assembly, in which a negative electrode plate and a positive electrode plate are wound in a predetermined shape, for example, a jelly-roll shape, with a separator interposed therebetween, a can, in which the electrode assembly and an electrolyte are accommodated, and a cap assembly coupled to an upper part of the can.
In this case, the negative electrode plate and the positive electrode plate may be formed by coating the active materials, that is, a negative electrode active material and a positive electrode active material, on the current collectors, for example, a negative electrode current collector and a positive electrode current collector, respectively.
However, the lithium rechargeable battery has a problem in that the active materials are deintercalated from the current collectors due to charging and discharging which are repeated several tens to several hundreds of times, so that battery efficiency deteriorates.